The present invention relates to pick-up truck cargo box covers (typically termed "tonneau covers" in the art), and more particularly to a tonneau cover and frame for removably attaching to the top perimeter of a pick-up truck cargo box.
Removable pick-up truck tonneau covers have been in existence for many years and generally comprise a flexible cover having male or female snap fasteners spaced about the peripheral edges thereof. Mating snap fasteners are usually mounted directly to the top, outer perimeter of the truck cargo box, or to a framework which is clamped to the top edge of the truck bed. The snap fasteners on the truck and cover must be in precise alignment to secure the cover to the truck bed, however, the flexible nature of the tonneau cover is subject to shrinkage and/or stretching over its surface by the elements such as sun, rain, snow, etc. This has been known to cause the male and female snap fasteners to go out of alignment thereby preventing proper securement of the tonneau cover to the truck bed. Various tonneau cover and truck bed frame fastening element designs have been developed in an effort to provide a tonneau cover and mounting frame which accommodates the changes in tonneau cover size due to uneven shrinking and stretching.
For example, U.S. Pat. No. 4,838,602 which issued to Nett on Jun. 13, 1989 discloses a tonneau cover frame having a longitudinally extending channel 38. A snap base 76 is pop riveted to a snap fastener glide 78 which is slidingly received in the channel 38. The top button 80 is fixedly secured to the peripheral edge of the tonneau cover with a snap fastener glide being slid along the frame channel to bring it into alignment with a respective cover top button which may then be releasably secured together.
U.S. Pat. No. 5,121,960, issued to Wheatly on Jun. 16, 1992 discloses three alternate structures and methods for releasably securing the tonneau cover to the frame. In two of the embodiments (FIGS. 4 and 12), a J-shaped, flexible fastener which resiliently engages the lip of the specialized frame is shown. In the other embodiment (FIGS. 8 and 9), a conventional male snap fastener 204 is fixed to a slider element 220 which rides along a track formed in the frame. Conventional female snap fasteners 202 which are provided in spaced relation along the peripheral edge of a tonneau cover are positioned over a respective one of the male fastener elements on the frame. Each male fastener element may be slid along the frame to bring it into alignment with a respective female fastener to be releasably secured to one another.
Lastly, U.S. Pat. No. 5,152,574, issued to Tucker on Oct. 6, 1992 discloses snap fastener "clips" carrying a male fastener element which are snapped on and off a track formed in the rail member. The clips may thus be repeatedly pried off and then repositioned on the rail member to bring it into alignment with a respective female fastening element on the cover.
In each of the above patents, the male fastening elements are subject to unintentional release from the rail whereupon they may be lost or misplaced. Furthermore, the male and female fastening elements must be repeatedly re-aligned by moving the individual male fastening elements along the rail which is necessarily a time-consuming task.